HAVANA (Reuters) - Three U.S. Democratic senators visiting Havana said on Tuesday that there could be enough Republicans who support lifting a trade embargo on Cuba to dismantle it in Congress.

The United States and Cuba agreed on Dec. 17 to restore diplomatic relations after more than five decades of hostility. U.S. President Barack Obama has already started to lift barriers to trade and travel.

Republican and Democratic senators have introduced two separate bills to lift travel restrictions on Americans going to Cuba and to repeal the 53-year-old embargo.

Although both bills face serious opposition in the Republican-controlled Senate and House of Representatives, they do have some Republican support from legislators such as Senator Jeff Flake, lead sponsor of the travel bill.

Democratic senators Claire McCaskill, Mark Warner and Amy Klobuchar concluded a four-day visit to Cuba on Tuesday and said they were optimistic about building bipartisan support for an end to the embargo.

Klobuchar is the lead sponsor of the embargo bill and a co-sponsor of the travel bill.

McCaskill said largely Republican agricultural interests in the Midwest supported lifting the embargo as "they really want to sell rice down here.

"So it is the business community and agricultural community who I think might have the most influence on helping us make this effort more bipartisan," McCaskill said.

Advocates for ending the embargo need 60 of 100 votes in the Senate and a majority in the House, where there are pockets of strong, mostly Republican opposition to Obama's new Cuba policy.

But McCaskill said opposition to other bills has been overcome when Speaker of the House John Boehner allows the entire House to vote on them.

"This could be one of those times, especially if the Chamber of Commerce and the commodities groups and the Farm Bureaus of the world really start putting political pressure on their own party," McCaskill said.

The U.S. Chamber of Commerce has long opposed the U.S. trade embargo as a violation of the principle that government should not impede free enterprise, also a tenet of the Republican Party.